Your body contains a large network of nerves, which carry electric signals to and from your brain. The signals going FROM the brain control your muscles so you can move around, talk, and keep your balance.
The signals going from your body TO the brain bring information about the outside world. As your brain processes this information, it allows you to see, to feel different sensations, and to hear, smell, and taste.
Together, your brain and spinal cord are known as your "central nervous system," or CNS.
The nerves that connect the central nervous system to the rest of the body are part of the "peripheral nervous system," or PNS.
Most nerves are covered by a fatty substance called "myelin." Myelin insulates the nerves and helps speed up the communication between your brain and other parts of your body. This keeps you functioning at a full level of activity.
If a nerve, or the myelin covering around it, becomes damaged, it can slow down or completely stop the electric signals. When this happens, it can impair your movement, sensations, or even your ability to think clearly.